1. Field of the Invention The present invention relates to an acid generating agent, and more particularly, to a salt useful as an acid generating agent contained in chemically amplified resist compositions that are used in semiconductor processes.
2. Description of the Related Art
A chemically amplified resist composition used in the semiconductor fine processing utilizing lithography contains an acid generating agent, and as the technologies supporting the semiconductor fine processing continue to develop, a demand for resists with higher resolution still exists.
Therefore, in order to produce a resist having an increased resolution and desired properties, a large number of different acid generating agents have been developed, and in particular, numerous modifications and experiments in design have been carried out concerning the cation part of salts that are used as photo-acid generating agents, so as to improve the diffusion rate of acid and transparency, which are important properties required from an acid generating agent.
However, in the recent research on resist compositions, the improvement of the properties of resist based on the cation of photo-acid generating agents is facing the limit, and there is rising another problem of reducing the amount of the salt of a photo-acid generating agent eluted into water, as water is used in the processes of argon fluoride (ArF) immersion lithography.
Therefore, in recent years, the development of acid generating agents is being achieved with more focus on the anion part, on the bases of numerous experimental results and reports showing that the anion moiety has substantially greater influence than the cation moiety in terms of the physical and chemical characteristics which can improve the fluidity of acid and the properties of the resist composition. Now, the trend of the development is inclined toward photo-acid generating agents which are capable of reducing the diffusion rate of acid, and have good transmissibility of ArF laser at 193 nm. Accordingly, there are competitive attempts to introduce a bulky alicyclic ring into the anion of a salt which is suitable as a photo-acid generating agent.